The invention relates to a fan apparatus for an electrical machine, with a fan, which can rotate around an axis and causes air to flow into the fan axially and out of the fan radially, a bearing plate, and a magnet wheel, in which a flow conduit is at least partially bounded by the bearing plate and the magnet wheel.
Operation of electrical machines naturally involves the generation of heat. It is desirable to dissipate this heat. Fans are frequently used for this purpose; they are supported so that they can rotate around the axis of the electrical machine. Upon rotation of the fan, air flows axially into the fan and radially out of the fan.
In generators that are used in motor vehicles, the housing is partially embodied as a bearing plate. Such a bearing plate extends radially outward from the bearing of a rotor shaft and then constitutes part of the axially extending outer surface of the generator. As a result, the bearing plate influences both the inflow and outflow of the cooling air.
It is disadvantageous that bearing plates of the prior art are embodied with sharp edges, which result in flow separations and turbulence. Such a disrupted flow generates noise and impairs the fan output.
FIG. 1 shows an apparatus including a fan 110 and bearing plate 112 of the prior art. The apparatus is part of a three-phase generator; only the upper half of the generator is partially depicted, extending to the center line 130. The lower half of the three-phase generator, which is not shown, is mirror symmetrical to the one shown. Air enters the fan 110 from the left in the vicinity of the fan inlet 132 and exits the fan in the radial direction in region 134. It is clear that before entry into the fan 110, the air must pass the bearing plate 112 so that influence is exerted on the air by the bearing plate 112 and in particular by the sharp edges that are generally present. The bearing plate 112 borders the air exit region 134 on one side and the magnet wheel 136 of the rotary current generator borders it on the other.
Since the distance between the bearing plate 112 and the magnet wheel 136 in the axial direction is constant, the flow cross section of the flow conduit 138 increases in the radial direction as a function of circular geometry. Consequently, the flow conduit 138 functions as a diffuser so that flow separations can occur. This impairs the fan output. Another disadvantageous effect of the apparatus including the fan 110 and bearing plate 112 of the prior art is that due to the distance between the fan 110 and the bearing plate 112, a recirculation flow 140 can occur. Since heated air consequently enters into the fan 110, this reduces the efficiency of the fan 110.